Method of making thermal



Patented 10, 1935 I Mn'rnon or MAKING THERMAL I msum'rron Martin ofnuggea, Evanston, n1;, assignor to Research, Inc., Chicago, 111., a corporation of Illinois No Drawing. Original application September 30, 1933, Serial No. 691,696. Divided and this an plication April 25, 1935, Serial No. 18,265

copending application, Ser. No. 691,696, filed Sep- 5v tember 30, 1933, on Thermal insulation, now Patent No. 2,001,912, dated May 21,1935.

It is an object of this invention to provide an improved method of making thermal insulation which is relatively simple and inexpensive in construction'and emcient in use,

Thermal insulation in the form of metal foil carried by a frame, and thermal-insulating sheets having a metallic heat-reflective surface or coating are well-known in the prior art as represented by the following patents: U. S. Patents Nos 1,757,479, 1,890,418, 10,375, 289,505, 294,780; 1,306,281, 1,383,680, 1,445,070, 1,667,691; British Patents Nos. 266,177 (1927) 310,572 (1929) 317,678 (1929); and German Patent No. 529,867

(1931). These patents pretty well represent the prior art in thermal insulation and they show the development-of thermal insulation including the use of thermal insulating sheets having a metallic coating thereon and functioning as the active, heat-reflective constituent thereof. There are, however, serious objections to, and difliculties experienced in the use of thermal insulation in the form of metal foil as well as in form of sheets having a metallic coating or heat-reflective surface. Among these objectionable features are: The usual form of metal used for thermal insulation and coatings therefor is either a metal foil carried by a frame or a metal powder spread upon a base sheet. These materials, however, are costly, brittle, and very fragile. In order to make them available for use'it is necessary to install them in rigid frames with the foil or coated sheet stretched and securely fastened in the frames. This construction is very impractical in building construction which requires a flexible, tough material which can be subjected, without damage, to rough handling, creasing, and abrasion.

Another objection to the prior art metal foils or metalliz ed heat insulation sheets is that their metallic content upon exposure to acids, alkalis, and atmospheric conditionscorrodes, tarnishes, and deteriorates generally, and thereby loses much of its heat-reflective power and efficiency. This is true whether the metallic insulation sheet be in the formof a metal foil or in the form of a foil-covered vegetable or cellulose base sheet or a base sheet having a metallic powder'spread thereover.

Objects of this invention, therefore, are; to provide a thermal insulating sheet which in use overcomes the aforementioned and other difficulties experienced in, the use of the prior heat insulators; to provide a thermal insulation sheet having a highly polished, silver-colored non-metallic coating or heat-reflective surface; and to.provide a 5 thermal insulation sheet that is relatively inextpensive to manufacture, which is flexible and tough, which can be subjected to rough handling and abrasion without damage; which is unaifected by weather conditions and the presence of 10 acids and alkalis; which can be creased and folded 4 without breaking or cracking its reflective surface; which is water proof and moisture-proof; and which is generally eflicient as a heat insulator inall of the uses to which it may be put. 15

The aforementioned objects may be accomplished and the hereinbefore referred to and pres- ,ent non-metallic heat insulation sheet produced in many different ways and by using many different formulas, or constituents, some of which will 20 be indicated hereinafter. However, a typical ex Formula and Example 1 25 A heat reflective coating or surface comprised of an intimate mixture of the following substances, the proportions indicated being by weight: 40 per cent finely divided silver sulphide 30 (AgzS) 40 per cent casein, and 10 per cent wax, maybe applied to a suitable vegetable base sheet which may be, for example, a sulphite or kraft paper or the like. This composition may be applied to. the base sheet in any'suitable manner 5 as by hand, by means of an automatic brush, known as a brush-coater; or by the rolls of a coating machine; or the adhesive casein maybe spread over the base sheet and the silver sulphide spread thereover as a dry powder as by 40 dusting, sifting, or spraying. The base sheet thus 'coated may then be placed in a friction calender struction where a thermal insulation sheet may bination of. kraft paper, sulphite paper, and.

ground wood; a combination of kraft paper, sulphite paper, ground wood, and waste mixed papers; or any combination of the above; or any fibrous material including silks, cottons, rayons, woolens, linens, or wood; or metal, glass orother surface.

As examples of other heat-reflective pigments or active constituents that may be used in the finely divided state-in place of silver sulphide in the manufacture of the aforementioned coating and heat-insulating sheet described in Example No. 1, as well as in the other coating compositions to be described hereinafter, are the following: litharge, aluminum oxide, stephanite, '(a silver antimony sulphide, AgzSbS), pyrargycite (AgSbS) horn silver (silver chloride, AgCl), in fusorial or diatomaceous earth, augite, a volcanic mineral of a black or greenish color, diallage, a mineral allied to augite having a brown, gray, or green color, laminated in structure, and having a metallic lustre when broken across; alunite, a boric sulphate of potassium and alum: inum, or any other heat-reflective substance which is non-metallic and which can be finely divided and highly polished to give a silver sheen. As examples of vehicles or carriers in which the silver sulphide in the above example, or any of the other heat-reflective constituents or pigments herein indicated may be used are: beeswax, paraflin wax, petroleum tailings,.china wax,

or any other wax whether itfbe soluble or insoluble in water, acid-resisting casein, or any casein in combination with formaldehyde; nitrocellulose; cellulose acetate; any phenol resin in combination with any asphalt derivative; any coal tar derivative; linseed oil or combinations thereof; starches; or any other vehicle that will act as an adhesive or binder and which will at the same time carry the aforementioned pigments or active heat-reflective constituents of the new heat-reflective coating composition and heat-insulating sheet. I

The heat reflective coating formula recited in Example 1, above, may be replaced by any of the following formulas, all proportions indicated being by weight unless otherwise specified:

Formula 2.--20 percent silver sulphide, finely divided; 60 percent casein in combination with formaldehyde; and from'5 per cent to 10 per -cent of a suitable wax, which may be any of those hereinbefore mentioned;

Formula 3 .-8 oz. of 60 second cotton; one quart of ethyl acetate; one quart of toluol; gal. of benzol or benzine mixed with castor'oil, tricresyl phosphate and butyl acetate; and 2 lbs. of finely divided silver sulphide or any of the other heat-reflective constituents or pigments herein indicated;

Formula 4.1 lb. of cumar; 10 per cent of soy bean oil; 20 per cent of naphtha; and 2 lbs. of

finely divided silver sulphide or other pigment hereinbefore named;

Formula 5.-3 lbs. of feculose casafin; 9 parts of water; one part of inverted sugar; and 2 lbs. of finely divided silver sulphide or other heat- 5 reflective pigment herein named; I

Formula 6.1 gal. of Chinawood oil; lb. of litharge; 2 lbs. of resin; and 1 galqof boiled linseed oil. This mixture is cooked to about 475 F. and the temperature allowed to drop to 10 about 350 F. A suitable quantity of naphtha is then added to the mixture; and finally to that mixture is added 1% to 2 lbsiof finely divided silver sulphide or any of the other non-metallic or mineral heat-reflective pigments hereinbefore 5 to one side or surface of a sheet of sulphite paper.

Two sheets of this sulphite paper thus coated are put through a duplexing machine with their uncoated surfaces back to back, and asphalt or other adhesive is applied to the untreated surfaces of the coated sulphite sheets; while simultaneously therewith a reenforcing fabric or web 0 or jute, flax, cotton, or metal is introduced between the sheets and thoroughly covered with asphaltum or other adhesive; and finally the two sheets having the reenforcing web therebetween are united by passing them between two rolls while applying sufficient pressure to form all of these materials into a single, homogeneous heat insulation sheet having highly effective heat-refleeting non-metallic coatings or surfaces on both sides thereof.

Product B.--This product is a heat insulation board particularly designed for use in building construction, and may be produced by coating one surface of a four or five ply pulpboard with any one of the above-named formulas. The process of manufacture is as follows: A heatrefiective surface coating is applied to chipboard, as above described, and this layer of chipboard, thus coated is then combined with three or four layers of the same material in the usual manner of combining or uniting pulpboard, or so-called wallboards, thereby leaving one heat-reflective surface exposed.

Product C".This product is an industrial insulation sheet particularly designed for use in the refrigeration industry and may be made by applying any one of the heat-reflective coating compositions above enumerated, and in the manner described, to one side of a suitable kraft paper, which may be paper of from 30 to 100 w lbs. weight, approximately.

The aforementioned products and uses illustrate the wide application and the variety of uses to which the new heat-insulating sheet may be put but they are illustrative rather than lirnita- 55 tive since the present heat-insulating sheet may also be used in many other ways and places, and

among which are:

For use in automobile tops and in the refrigeration industry where tests of its use show considerable reductions in ice and electricity consumption when using this product; .and as a heat-refiective surface behind or in back of radiators; while any one of the aforementioned coating compositions itself may be applied to sheet metal in the manufacture of radiator cabinets. When so used the coating composition adds greatly to products may also be used for porch screens,

sun-room screens, window screens, arranged be-.

hind plate glass to prevent frost accumulation; as window shades to reflect the sun's heat and to prevent it-from entering a room or building; and in other ways.

Experimental data in the applicant's possession, and made upon test samples of certain of the products hereinbefore named, show that these products are effi'cient heat insulators; that their heat conductivity is less than, and consequently their heat insulating efficiency greater than, the usual vegetable board or sheet insulators, and metallic foil or metal-coated insulators now in use.

By way of recapitulation it may, therefore, be saidthat the present invention contemplates essentially a heat-insulating and reflective sheet consisting of a base having a highly polished, heat-reflective coating spread thereover and the heat-reflective coating consisting essentially of an adhesive vehicle or carrier having incorporated therein a finely divided, non-metallic substance which is capable of being highly polished to provide a bright, silver-colored heat-reflective surface.

By the term non-metallic as used hereinbefore, andfas used hereinafter in the claims, is

meant any substance other than a metal, that is, other than a'simple elementary metal such, for example, as aluminum foil or powder, but in.- cluding mineral, as well as non-mineral substances and vegetable and mineral substances, 5 which is capable'of being finely divided and spread upon and adhered to a'base or base sheet, and which can be highly polished to provide a bright, silver-colored heat-reflective surface.

Having thus described my invention, what I 10 claim as new and desireto protect by Letters Patent is: a

'1. The method of making thermal insulation which consists in securing a flli'n oi non-metallic,

mineral material having relatively little or no 15 lustre but including a binder to a supporting base sheet and then subjecting the said film to friction at an elevated temperature and pressure so as to convert the same into a highly polished, heatreflective. surface whose heat-reflective power go 

